1. Technical Field
The present invention relates to gas turbine engine fasteners and, more particularly, to gas turbine engine fasteners for attaching components fabricated from dissimilar materials.
2. Background Art
A typical gas turbine engine operates in an extremely harsh environment characterized by very high temperatures and vibrations. A conventional gas turbine engine includes a compressor for compressing entering air, a combustor for mixing and burning the compressed gases that emerge from the compressor with fuel, a turbine for expanding the hot gases to generate thrust to propel the engine, and an exhaust nozzle for allowing hot gases to exit the engine. Thus, the exhaust nozzle must accommodate extremely hot gases exiting the engine.
In military operations, design of planes to avoid detection by radar has become an important issue. The ability of the plane to remain undetected, also referred to as a signature of a plane, depends on the overall geometry of the plane and materials the plane is fabricated from. To minimize detection, it is preferable to eliminate gaps between engine parts and to achieve certain smoothness for the outer shape of the engine. Additionally, it is preferable to avoid use of metals on the outer surfaces of the engine.
Other considerations critical to engine design are avoiding air leakage and insulating certain engine components from exposure to hot gases. One type of a material that withstands hot temperatures is ceramic matrix composite (or CMC), material. However, it is difficult to attach the CMC material components to metal components. One obstacle to attaching the CMC material to the metal is different thermal expansions of the materials. In general, it is difficult to attach or join different materials in a gas turbine engine due to different thermal expansion properties.